Radio frequency or RF energy is commonly used in a variety of different surgical operations. However, body tissues that are subjected to very high levels of RF energy may suffer some residual heat damage. Therefore, prior to the use of RF energy on a particular patient it is often desirable to develop computer simulated heat transfer and electric field models of the heat transfer to tissue using computer programs.
When an electric charge is applied across a material, in this case tissue, a charge and current are created in the material. The density of charge is referred to as the permittivity (∈) while the density of current is called the conductivity (σ). These two properties are largely responsible for the response of different tissue types to an arbitrary RF electric field and should be included in any accurate computer modeling. Moreover, by comparing the electrical properties of healthy and abnormal tissue it may be possible to detect the onset of certain kinds of pathologies or sicknesses.
Testing methodologies exist for determining the permittivity and conductivity of a given material. However, a number of these methodologies contain numerous sources of error that affect the accuracy of the measurement, which may be detrimental to accurate tissue heat transfer modeling.